EGFRvIII peptide, a synthetic peptide mirroring the EGFRvIII fusion junction—a tumor-specific, perpetually active EGFR variant missing amino acids 6-273 of the wild-type—binds to HLA-A*0201-positive T2 cells under MHC class I at 25 µg/ml. It enables antigen presentation in dendritic cells from human peripheral blood mononuclear cells (PBMCs), thus activating CD8+ cytotoxic T lymphocytes and prompting IFN-γ production. Administered at 15 µg/animal with the TLR5 agonist flagellin B, EGFRvIII peptide elevates CD8+ T cell numbers, lowers regulatory T cells (Tregs) in the brain, diminishes tumor volume, and extends survival in a GL261 glioblastoma mouse model.